Image reading apparatus, image reading method and a program for measuring black and white reference data

ABSTRACT

A carriage motor which is a heat generating device is arranged next to a CIS in a scanner unit. The carriage motor drives respective transport rollers of an ADF unit via a gear system as well. The scanner unit makes a white reference board be read so as to obtain white reference data, and obtains black reference data more frequently than the white reference data, e.g., in a continuous process for reading a document. As a CIS module continues a reading process, the black reference data changes as being affected by a change in temperature in the CIS module, etc. The scanner unit deals with such a change in the black reference data by obtaining the black reference data more frequently.

INCORPORATED BY REFERENCE

The entire disclosure of Japanese Patent Application No. 2012-028104,filed Feb. 13, 2012 is expressly incorporated by reference herein.

BACKGROUND

1. Technical Field

The present invention relates to an image reading apparatus, an imagereading method and a program.

2. Related Art

An image reading apparatus which stores black reference data in advance,measures only white reference data in time of reading a document, anduses the black reference data having been stored in advance and themeasured white reference data for shading correction to image dataproduced from the read document is proposed in recent years, e.g., asdisclosed in JP-A-2005-94135. The apparatus stores the black referencedata to be used for shading correction before reading the document so asto further control a delay in starting to read the document.

Incidentally, the image reading apparatus according to JP-A-2005-94135described above is aimed at carrying out a process for reading adocument faster. Black reference data read by an image reading apparatusmay conceivably change in some cases depending upon a configuration or areading method of the image reading apparatus. Thus, enhancement ofimage quality produced from a read document is desired.

SUMMARY

An advantage of some aspects of the invention is to provide an imagereading apparatus, an image reading method and a program which can eachenhance image quality further when carrying out a process for reading adocument.

The invention is formed by including following sections so as to achievethe above advantage.

An image reading apparatus of the invention includes a transport sectionconfigured to transport a document; a reading section configured to readthe transported document in a transport reading region; a whitereference material arranged at a position to be read by the readingsection; and a control section configured to control the transportsection and the reading section so as to obtain white reference data bymaking the reading section read the white reference material and toobtain black reference data more frequently than the white referencedata.

The image reading apparatus makes the white reference material be readso as to obtain the white reference data and obtains the black referencedata more frequently than the white reference data. The black referencedata read by the reading section may conceivably change, e.g., as thereading section continues a reading process. The control section dealswith such a change in the black reference data by obtaining the blackreference data more frequently. The control section can thereby enhancean image quality further when carrying out a process for reading adocument.

The reading section of the image reading apparatus of the invention mayadjoin a movable section which moves while generating heat when thereading section reads the document. As the reading section continues areading process, the movable section generates heat resulting in achange in the black reference data. Thus, the control section canthereby control degradation of the image quality caused by the heatgeneration further so as to enhance the image quality further. At thistime, the movable section may be a driving motor which drives thetransport section. As the driving motor generates relatively much heat,the invention is worthy of being applied. At this time, the drivingmotor may be used as a driving motor which is coupled by a couplingsection and drives the transport section so as to move the readingsection as well. As the driving motor generates much more heat close tothe reading section in such a structure while the document to be read isindispensably being transported, the invention is further worthy ofbeing applied.

The control section of the image reading apparatus of the invention mayobtain the black reference data in the transport reading region wherethe transported document is read. The control section can therebyfurther shorten a period of time for moving the reading section whichmay arise as the black reference data is much frequently obtained, andthus can further enhance the image quality while further controllingextension of processing time.

The white reference material of the image reading apparatus of theinvention may be arranged opposite the transport reading region over astatic reading region where a document being put still is read, and thecontrol section may read the black reference data in the transportreading region. As the reading section thereby moves to the whitereference material arranged apart less frequently, the control sectioncan further enhance the image quality while further controllingextension of processing time.

The control section of the image reading apparatus of the invention mayobtain the black reference data more frequently by obtaining the blackreference data upon a specific period of continuous reading time passingin a process for reading the document. The control section can therebyobtain the black reference data more frequently so as to further enhancethe image quality. The specific period of continuous reading time may bedetermined, e.g., as a period of time in which degradation of an imagequality whose relationship with a continuous process for reading adocument is empirically obtained stays allowable.

The control section of the image reading apparatus of the invention maycontrol the transport section and the reading section so as to read thedocument with a plurality of values of resolution including a specifichigh frequency resolution value, obtain the white reference data and theblack reference data when the resolution value with which the documentis read excepts the high frequency resolution value, and obtain theblack reference data when the resolution value with which the documentis read is the high frequency resolution value. The control section canthereby further enhance the image quality while further controllingextension of processing time. The high frequency resolution value maybe, e.g., one to be used in a process for reading a document morefrequently than other resolution values. The control section can therebyobtain the white reference data less frequently with a resolution valueof a high frequency so as to further enhance the image quality whilefurther controlling extension of processing time.

The control section of the image reading apparatus of the invention maycontrol the transport section and the reading section, upon specific lowpower performance conditions being satisfied, in relevant low powerconditions, and obtain the white reference data and the black referencedata when returning from the low power conditions. The control sectioncan thereby further enhance the image quality by obtaining new whitereference data and black reference data upon returning from the lowpower conditions.

Incidentally, the image reading apparatus of the invention may have ashading correction running section configured to run shading correctionin the process for reading a document by using the white reference dataand the black reference data.

An image reading method is one that a computer performs by using animage reading apparatus having a transport section configured totransport a document, the image reading apparatus having a readingsection configured to read the transported document in a transportreading region, the image reading apparatus having a white referencematerial arranged at a position to be read by the reading section. Theimage reading method includes (a) a step for controlling the transportsection and the reading section so as to obtain white reference data bymaking the reading section read the white reference material and toobtain black reference data more frequently than the white referencedata.

According to the image reading method, similarly as to the image readingapparatus described above, the black reference data may conceivablychange as the reading section continues a reading process. The imagereading apparatus to be used for this method obtains the black referencedata more frequently and deals with the change in the black referencedata, though, so that the image quality can further be enhanced.Incidentally, various forms of the image reading apparatus describedabove may be employed for the image reading method. Further, a step forputting each of functions of the image reading apparatus described aboveinto practice may be added to the image reading method.

A program of the invention is such that one or more computers run stepsof the image reading method described above. The program may be storedin a computer-readable recording media (e.g., hard disk, ROM, FD, CD,DVD, etc.), may be disseminated from one computer to other computers viaa transfer medium (network such as the Internet or a LAN), or may betransmitted and received in any form. If one computer is made run theprogram or plural computers are made run respective steps into which theprogram is divided, the respective steps of the image reading methoddescribed above are run so that a same effect as that of the imagereading method can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a structural diagram which schematically illustrates astructure of a multifunction printer.

FIG. 2 is a structural diagram which schematically illustrates astructure of a scanner unit.

FIG. 3 is a flowchart which shows an exemplary main processing routine.

FIG. 4 is a flowchart which shows an exemplary image reading processingroutine.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Then, an embodiment of the invention will be explained by the use of thedrawings. FIG. 1 is a structural diagram which schematically illustratesa structure of a multifunction printer 20, an embodiment of theinvention. FIG. 2 is a structural diagram which schematicallyillustrates a structure of a scanner unit 40.

The multifunction printer 20 of the embodiment is formed by a housing 21and a housing cover 22 which can open or close a top face of the housing21. The multifunction printer 20 has a scanner unit 40 which opticallyreads a document and produces image data, a printer unit 42 which feedspaper set in a cassette 23, does printing and ejects paper to a paperejection tray 24, an operation panel 46 that a user can variouslyoperate, and a main controller 80 which entirely controls the apparatus.The housing 21 is provided with a flatbed portion 31 having a glassplate 32 on the top face. The scanner unit 40 is configured to opticallyread a document put on the glass plate 32 (this operation mode is calleda fixed document reading mode hereafter). Further, the housing cover 22contains an auto document feeder unit 61 (called ADF unit hereafter)(see FIG. 2), and the scanner unit 40 is configured, while automaticallyand successively transporting document sheets having been set at an ADFslot 26 along a document guide 29, to optically read the document sheets(this operation mode is called an ADF reading mode hereafter).

The scanner unit 40 has a scanner ASIC 50 and a scanner engine 60. Thescanner ASIC 50 is an integrated circuit which controls the scannerengine 60. Upon receiving instructions to scan from the main controller80, the scanner ASIC 50 controls and instructs the scanner engine 60 toread a document as image data either in the fixed document reading modeor in the ADF reading mode.

The scanner engine 60 has an ADF unit 61 which automatically transportsa document S set at the ADF slot 26 into an ADF reading region 34, alight source unit 71 which irradiates the glass plate 32 or the ADFreading region 34 with light, a contact image sensor (CIS) 74 whichreads the document S by receiving light reflected by the document S andstoring the received light as electric charges, a CIS module 76 on whichthe light source unit 71 and the CIS 74 are installed, a carriage motor78 which is fixed below a housing of the CIS module 76 and moves withthe CIS module 76 together, a motor gear 78 a to be driven to rotate bythe carriage motor 78, and a guide gear 79 arranged in a sub scandirection. The motor gear 78 a meshes with the guide gear 79, and a moveof the CIS module 76 is controlled in the sub scan direction in whichthe guide gear 79 is arranged. That is, the CIS module 76 is configuredto move back and forth in the sub scan direction along the guide gear 79as being driven by the carriage motor 78. The carriage motor 78 is astepping motor which moves the CIS module 76 line by line in time ofreading by the CIS module 76, and works while generating heat. Thecarriage motor 78 is arranged next to the CIS 74. The ADF unit 61 has apickup roller 63 arranged close to the ADF slot 26, a plurality oftransport rollers 64 arranged on a transport path 62, and a paperejection roller 65 arranged close to the ADF paper ejection tray 28. Thelight source unit 71 has a three-color light source formed by a red LED72R, a green LED 72G and a blue LED 72B which emit red, green and bluelight, respectively, as shown in FIG. 1. The light source unit 71irradiates the glass plate 32 or the ADF reading region 34 with lightcoming from the light source via an optical waveguide 73. The CIS 74 isformed by a plurality of photo-detectors (CMOS image sensors) 75 for oneline arranged in a main scan direction. The CIS 74 produces color imagedata by reading reflected light color by color while turning on the LEDs72R, 72G and 72B of the respective colors alternately one by one.

The scanner engine 60 is configured in such a way that, if the CISmodule 76 is placed in the ADF reading region 34 as shown in FIG. 2, agear system 77 coupled with the respective rollers for transportationsuch as the pickup roller 63, the transport rollers 64 and the paperejection roller 65 of the ADF unit 61 meshes with the motor gear 78 a.If the carriage motor 78 is driven in the ADF reading region 34 so thatthe CIS module 76 moves to the left in FIG. 2, the motor gear 78 ameshes with nothing on the side of the guide gear 79 and meshes with thegear 77 on the side of the gear 77 so that driving force is transferredto the ADF unit 61. The ADF unit 61 takes in document sheets set at theADF slot 26 sheet by sheet and automatically transport the documentsheets onto the transport path 62 by driving the respective rollers fortransportation to rotate by means of the driving force of the carriagemotor 78 in this way. That is, the carriage motor 78 is configured to beused as motors for moving the CIS module 76 and for transporting thedocument S together. The configuration is simplified in this way.

The scanner ASIC 50 has a reading processor 51 which controls respectivedevices, an LED driver 54 which turns the LEDs 72R, 72G and 72Bindividually on or off, an A/D converter 56 which is provided with ananalog signal produced by the CIS 74 via an amplifier which is not shownand converts the analog signal into a digital signal, and a motor driver58 which drives the carriage motor 78 upon receiving a control signalfrom the reading processor 51. The reading processor 51 has a controller52 and a shading correction processor 53. The controller 52 has afunction to obtain white reference data W and black reference data K tobe used for shading correction as well as a function of a process forreading the document S. The shading correction processor 53 has afunction to carry out a shading correction process. The shadingcorrection process is a series of data processing to remove densityunevenness caused pixel by pixel by variation of light emission by thelight source unit 71, variation of element by element sensitivitycharacteristics of the photo-detectors 75, a change in the electriccharges dependent on temperature in the CIS 74, etc., by using the blackreference data K and the white reference data W (shading correction).The scanner unit 40 has a white reference board 36 arranged opposite theADF reading region 34 over the glass plate 32 which is a static readingregion, i.e., at an end portion in the sub scan direction. The blackreference data K is an output voltage obtained by the photo-detectors 75in case of a scan in condition such that the CIS module 76 is placed inthe ADF reading region 34 (or opposite the white reference board 36) andthat all light sources are turned off. Further, the white reference dataW is an output voltage obtained by the photo-detectors 75 in case of ascan in condition such that the CIS module 76 is placed opposite thewhite reference board 36 and the LEDs 72R, 72G and 72B of the respectivecolors are turned on.

The printer unit 42 has a printer ASIC 44 and a printer engine 45. Theprinter ASIC 44 is an integrated circuit which controls the printerengine 45. Upon being instructed to print by the main controller 80, theprinter ASIC 44 controls the printer engine 45 so that an image isprinted on a sheet of recording paper on the basis of an image file tobe instructed to print. The printer engine 45 is configured to print byemitting ink from a printing head onto a sheet of paper as a colorprinter mechanism according to a known ink jet system. Incidentally, asthe printer unit 42 is not included in the gist of the invention, afurther detailed explanation of it will be omitted.

The operation panel 46 has a display monitor 47 arranged in the middleand a power button 48 arranged to the immediate left of the displaymonitor 47. The display monitor 47 is formed as a liquid crystal displayof a touch panel system. The display monitor 47 displays a mode buttonfor mode selection, a selection/setting button for menu or itemselection to be touched according to a guidance shown on the display, astart button to start copying or printing, etc., and accepts a touchoperation. Modes which can be selected by the use of a mode selectionbutton are a copy mode in which a document put on the glass plate 32 isscanned and copied, a memory card mode in which printing is done by theuse of an image stored in a memory card MC that a memory card slot 49 isloaded with or a document is scanned and converted into data to bestored in the memory card MC, a film mode in which a photo film isscanned and printed or data is stored in the memory card MC, etc.

The main controller 80 is formed as a microprocessor centered on a CPU82, and has a flash memory 84 in which various data processing programs,various kinds of data, various kinds of tables, etc., are stored, a RAM86 in which scan data or printing data is temporarily stored, and aninternal communication interface 88 which enables communication with theoperation panel 46. The main controller 80 is configured to be providedwith various kinds of operation or detection signals coming from theprinter unit 42 or the scanner unit 40, or with an operation signalproduced in response to a touch operation done on the operation panel46. Further, the main controller 80 is configured to read an image filefrom the memory card MC, to instruct the printer unit 42 to print imagedata, to instruct the scanner unit 40 to read a document put on theglass plate 32 as image data on the basis of scan instructions comingfrom the operation panel 46, or to output instructions to control thedisplay monitor 47 to the operation panel 46.

Then, how the scanner unit 40 of the embodiment formed as describedabove works, particularly in case of a scan in the ADF reading mode,will be explained. FIG. 3 is a flowchart which shows an exemplary mainprocessing routine to be run by the CPU 82 of the main controller 80.FIG. 4 is a flowchart which shows an exemplary image reading processingroutine to be run by the scanner ASIC 50. Suppose here, for a mainexplanation, that a user sets sheets of a document S at the ADF slot 26and presses a start button which is displayed on the operation panel 46but is not shown so that the plural sheets of the document S aresuccessively read. The main processing routine is a processing routineto be run by the scanner unit 40, and is run, e.g., after the userpresses the power button 48 and the apparatus is powered on.

Upon running the routine, the CPU 82 runs a process for obtaining thewhite reference data W with a specific high frequency resolution value(step S100). The scanner unit 40 can carry out a process for reading thedocument S with plural resolution values for reading, e.g., 300, 600,1200 dpi, etc. Among these resolution values for reading, a resolutionvalue frequently used by the user (e.g., 600 dpi) is specified as a highfrequency resolution value. Further, suppose that the scanner unit 40makes the CIS module 76 move from a home position (on the right of thewhite reference board 36 in FIG. 2) towards the white reference board 36in the process for obtaining the white reference data W, and runs aprocess to read the white reference board 36 by means of the CIS module76 with light emission by the light source unit 72 together. The whitereference data W is stored immediately after the apparatus is powered onas to the frequently used resolution value for reading in this way.

Then, the CPU 82 decides whether or not a scan is requested on the basisof an input signal coming from the operation panel 46 (step S110). If noscan is requested, the CPU 82 decides whether low power performanceconditions in which the apparatus shifts into a specific low power modeare satisfied (step S150). The low power mode is a mode for controllingpower consumption of the main controller 80, the carriage motor 78,etc., on a side of lower power compared with conditions in which thedocument S is read. Suppose that the low power performance conditionsare satisfied if, e.g., the multifunction printer 20 has not beeninstructed to print or to scan for a particular period of time (such astwo, five or ten minutes). If the low power performance conditions aresatisfied, the scanner unit 40 controls the respective units in the lowpower mode (step S160). Unless the low power performance conditions aresatisfied, the scanner unit 40 controls the respective units in aregular power mode (step S170). The CPU 82 decides whether the apparatusis powered off after the step S160 or S170 (step S180). Unless theapparatus is powered off, the CPU 82 carries out the process at andfollowing the step S110.

Meanwhile, if a scan is requested at the step S110, the CPU 82 decideswhether a current operation mode is the low power mode (step S120). Ifit is the low power mode, the CPU 82 carries out a process for returningfrom the low power mode to the regular power mode (step S130). Then, thescanner unit 40 carries out a process for reading images on the sheetsof the document S (step S140), and carries out the process at andfollowing the step S150 described above. Then, the routine ends upon theapparatus being powered off at the step S180.

The image reading process at the step S140 will be explained below indetail. The image reading process is carried out by the use of therespective functions such as the reading processor 51, the controller52, the shading correction processor 53, the LED driver 54, the A/Dconverter 56 and the motor driver 58. Upon the routine being carriedout, the scanner ASIC 50 decides a reading mode in which the document isread (step S200). If the reading mode is an FB reading mode, the scannerASIC 50 obtains the white reference data W and the black reference dataK (step S210). Suppose here that the scanner ASIC 50 carries out aprocess for obtaining the white reference data W at a position oppositethe white reference board 36 by means of the CIS module 76, andobtaining the black reference data K by means of the CIS module 76 atthe same position in dark conditions where no light is radiated. Then,the scanner ASIC 50 carries out a process for reading the document S onthe flatbed portion 31 (step S270), carries out shading correction (stepS280), and carries out a process for storing obtained image data onwhich the shading correction and other image processing is done (stepS290). Suppose that the shading correction processor 53 carries out aknown process for correcting a pixel value read by the CIS 74 by usingthe white reference data W and the black reference data K in the shadingcorrection process. Then, the scanner ASIC 50 decides whether theprocess is finished (step S300), and ends the routine upon the processbeing finished.

Meanwhile, if the reading mode is the ADF reading mode, the scanner ASIC50 decides whether the apparatus has returned from the low power mode(step S220). If the apparatus has returned from the low power mode, thescanner ASIC 50 carries out the process at and following the step S210,i.e., obtains the white reference data W and the black reference data Kand carries out the process for reading the document S. A reason why isthat significant time has conceivably passed since the process forreading the document S was carried out last time, and that it ispreferable for enhancement of a read image quality to obtain latestwhite and black reference data K and W. Incidentally, suppose in theprocess at the step S210 that the scanner ASIC 50 carries out a processfor obtaining the white reference data W at the position opposite thewhite reference board 36 by means of the CIS module 76, then moving theCIS module 76 to the ADF reading region 34 and obtaining the blackreference data K in dark conditions where no light is radiated.

Meanwhile, unless the apparatus has returned from the low power mode,the scanner ASIC 50 decides whether a first sheet is currently beingread in the process (step S230). If a first sheet is currently beingread in the process, the scanner ASIC 50 decides whether the specifichigh frequency resolution value is applied to the current process forreading the document on the basis of scan setting conditions set by theuser (step S240). If the high frequency resolution value is applied, thescanner ASIC 50 obtains the black reference data K (step S250) as havingobtained the white reference data W at the step S100 in the mainprocessing routine described above. Suppose here that the CIS module 76is placed in the ADF reading region 34 and that the scanner ASIC 50carries out a process for obtaining the black reference data K by meansof the CIS module 76 in dark conditions where no light is radiated.Then, the scanner ASIC 50 can carry out a process for reading thedocument S in the ADF reading region 34 without any change in theconditions. Further, it is unnecessary to move to the white referenceboard 36 to obtain the white reference data W. Meanwhile, unless thespecific high frequency resolution value is applied at the step S240,the scanner ASIC 50 obtains the white reference data W and the blackreference data K together at the step S210 as neither white referencedata W nor black reference data K is available. Suppose here that thescanner ASIC 50 carries out a process for obtaining the white referencedata W at the position opposite the white reference board 36 by means ofthe CIS module 76, then moving the CIS module 76 to the ADF readingregion 34 and obtaining the black reference data K. The scanner ASIC 50carries out the process at and following the step S270 after the stepS250 or S210. That is, the scanner ASIC 50 makes the ADF unit 61transport the document S, reads the document S by means of the CISmodule 76, and carries out a process for producing image data whilecarrying out shading correction by using the white reference data W andthe black reference data K. If the document S include lots of sheets,etc., temperature may rise in the CIS 74 in some cases because of heatgeneration by the carriage motor 78 arranged close to the CIS 74 anddriven when the document S is transported.

Meanwhile, unless a first sheet is currently being read in the processat the step S230, i.e., one of second and following sheets is currentlybeing read in the process, the scanner ASIC 50 decides whether theprocess for reading the document S has continued for a specific periodof continuous reading time and over (step S260). The specific period ofcontinuous reading time may be determined, e.g., as a period of time forwhich degradation of an image quality whose relationship with acontinuous process for reading the document S is empirically obtainedstays allowable. Incidentally, the “continuous process for reading thedocument S” means, e.g., it can be decided that the controller 52 iscontinuously carrying out the reading process even if temperatureinconspicuously falls in the carriage motor 78 in some interval. Then,unless the process for reading the document S has continued for thespecific period of continuous reading time and over, the scanner ASIC 50carries out the process at and following the step S270 by continuouslyusing the previously obtained white reference data W and black referencedata K. That is, the scanner ASIC 50 makes the ADF unit 61 transport thedocument S, read the document S by means of the CIS module 76, andcarries out a process for producing image data while carrying outshading correction by using the white reference data W and the blackreference data K. Meanwhile, if the process for reading the document Shas continued for the specific period of continuous reading time andover at the step S260, the scanner ASIC 50 obtains the black referencedata K at the step S250 and carries out the process at and following thestep S270. As latest black reference data K is obtained, the scannerASIC 50 can more certainly correct so called black floating caused by arise in temperature in the CIS 74 when the carriage motor 78 iscontinuously driven, etc. Further, as obtaining only the black referencedata K, the scanner ASIC 50 can further control the move towards thewhite reference board 36 and can shorten processing time. The scannerASIC 50 obtains the black reference data K more frequently than thewhite reference data W in accordance with heat generation by thecarriage motor 78. Then, if the process ends at the step S300, thescanner ASIC 50 ends the routine.

Relationships between the respective portions of the embodiment andportions of the invention corresponding to each other are disclosedbelow. The ADF unit 61 of the embodiment corresponds to a transportsection of the invention. The CIS module 76 corresponds to a readingsection. The scanner ASIC 50 corresponds to a control section. Thecarriage motor 78 corresponds to a movable section. The ADF readingregion 34 corresponds to a transport reading region. The glass plate 32corresponds to a static reading region. Incidentally, an operation ofthe scanner unit 40 of the embodiment is explained, so that an exampleof an image reading method of the invention is disclosed.

The scanner unit 40 of the embodiment described above in detail makesthe white reference board 36 be read so as to obtain the white referencedata W and obtains the black reference data K more frequently than thewhite reference data W. The black reference data K changes as beingaffected by a change in temperature in the CIS module 76 as the readingprocess by the CIS module 76 continues. The scanner unit 40 deals withsuch a change in the black reference data K by obtaining the blackreference data K more frequently. The scanner unit 40 can therebyenhance an image quality further when carrying out a process for readingthe document S. Further, the carriage motor 78 which works with heatgeneration when the document S is read is arranged next to the CIS 74.Although heat generation by the carriage motor 78 causes a change in theblack reference data K as the reading process continues, the scannerunit 40 can further enhance the image quality by further controllingdegradation of the image quality caused by the heat generation byobtaining the black reference data K more frequently. Further, as thecarriage motor 78 generates relatively much heat, the invention isworthy of being applied. Further, as being coupled by the gear system 77and used as a motor for transporting the document S in the ADF unit 61as well, the carriage motor 78 generates more heat close to the CIS 74when the document S is transported. Thus, the invention is furtherworthy of being applied.

Further, as the black reference data K is obtained in the ADF readingregion 34 where the document S is read, it does not take a long time forthe CIS module 76 to move which could arise as the black reference dataK is obtained. The scanner unit 40 can thereby enhance the image qualityfurther while further controlling extension of the processing time.Further, the white reference board 36 is arranged opposite the ADFreading region 34 over the glass plate 32, and the scanner unit 40obtains the black reference data K and the white reference data W in theADF reading region 34 and at the position opposite the white referenceboard 36, respectively. Thus, the CIS module 76 moves towards the whitereference board 36 arranged apart less frequently, and the scanner unit40 can further enhance the image quality while further controllingextension of the processing time. Still further, while obtaining thewhite reference data W and the black reference data K when the documentis read with resolution excepting the high frequency resolution value,the scanner unit 40 obtains only the black reference data K in case ofthe high frequency resolution value. The scanner unit 40 can therebyfurther enhance the image quality while further controlling extension ofthe processing time in case of the high frequency resolution value.Further, the high frequency resolution value is used in a process forreading a document more frequently than other resolution values. Thus,upon obtaining the white reference data less frequently in a readingprocess with resolution of a high frequency, the scanner unit 40 canfurther enhance the image quality while further controlling extension ofthe processing time. Then, as obtaining the black reference data K ifthe process for reading the document has continued for the specificperiod of continuous reading time and over, the scanner unit 40 canfurther enhance the image quality by obtaining the black reference dataK much frequently in a continuous process for reading a document. Stillfurther, as obtaining the white reference data W and the black referencedata K when returning from low power conditions, the scanner unit 40 canfurther enhance the image quality.

Incidentally, it goes without saying that the invention is not at allrestricted by the embodiment described above, and that the invention canbe put into practice in various forms as long as such a variation stayswithin the scope of the invention.

It is assumed, e.g., that the carriage motor 78 which generates heat andthe CIS 74 of the embodiment described above are arranged next to eachother. As long as obtaining the black reference data K more frequentlythan the white reference data W, the scanner unit 40 is not restrictedby such a structure. As the black reference data K sometimes changesbecause of a factor excepting the heat generation, the scanner unit 40can further enhance the image quality by obtaining the black referencedata K more frequently regardless of whether or not a device whichgenerates heat is next to the CIS module 76.

Although being assumed to obtain the black reference data K in the ADFreading region 34 as to the embodiment described above, the scanner unit40 is not restricted by such a configuration. The scanner unit 40 mayobtain the black reference data K, e.g., at the position opposite thewhite reference board 36. The scanner unit 40 can thereby enhance theimage quality further at the cost of longer processing time.Incidentally, it is more preferable to obtain the black reference data Kin the ADF reading region 34 because of shorter processing time.

Although it is assumed that the white reference board 36 is arrangedopposite the ADF reading region 34 over the glass plate 32, the scannerunit 40 is not restricted by such a structure. The white reference board36 may be arranged, e.g., next to the ADF reading region 34.Incidentally, it is more preferable to arrange the white reference board36 opposite the ADF reading region 34 over the glass plate 32 uponrelative home positions, light shielding characteristics and downsizingof the entire apparatus being considered.

Although having one value as to the embodiment described above, the highfrequency resolution may have two or more values. Further, the scannerunit 40 may obtain white reference data W of resolution having two ormore values at the step S100. Otherwise, the scanner unit 40 may obtainno white reference data W at the step S100. That is, the setting of thehigh frequency resolution may be omitted.

Although being assumed to obtain the black reference data K if thespecific period of continuous reading time has passed as to theembodiment described above, the scanner unit 40 is not restricted bysuch a configuration upon obtaining the black reference data K morefrequently than the white reference data W. Use of the specific periodof continuous reading time may be omitted. Even so, the scanner unit 40can further enhance the image quality by obtaining the black referencedata K more frequently.

Although being assumed to obtain the white reference data W and theblack reference data K upon returning from the low power conditions, thescanner unit 40 is not restricted by such a configuration. Further, thelow power conditions may be omitted.

Although being explained as the multifunction printer 20 of theembodiment described above, the apparatus is not limited to that as longas the apparatus performs shading correction by using the whitereference data W and the black reference data K. The apparatus may be,e.g., a scanner apparatus lacking the printer unit 42, or a facsimileapparatus having a facsimile function. Further, although being assumedto be a color printer mechanism according to an ink jet system, theprinter unit 42 is not limited to that and may be a color printer of anelectronic photo system, a color printer of a dot impact system, or amonochrome printer of those systems.

The multifunction printer 20 of the embodiment is explained above. Theembodiment may be similarly explained as an image reading method or aprogram to carry out the method.

1. An image reading apparatus comprising: a transporter configured totransport a document; a reader configured to read the transporteddocument in a transport reading region; a white reference materialarranged at a position to be read by the reading section; and acontroller configured to control the transport section and the readingsection so as to obtain white reference data by making the readingsection read the white reference material and to obtain black referencedata, wherein, the controller obtains the white reference data when theage reading apparatus returns from low power mode, and the controllerdoes not obtain the white reference data when the image readingapparatus has been a normal power mode.
 2. The image reading apparatusaccording to claim 1, wherein the reading section adjoins a movablesection which moves while generating heat when the reading section readsthe document.
 3. The image reading apparatus according to claim 1,wherein the control section obtains the black reference data in thetransport reading region where the transported document is read.
 4. Theimage reading apparatus according to claim 1, wherein the whitereference material is arranged opposite the transport reading regionover a static reading region in which a document being put still isread, and the control section obtains the black reference data in thetransport reading region.
 5. The image reading apparatus according toclaim 1, wherein the control section obtains the black reference datamore frequently by obtaining the black reference data upon a specificperiod of continuous reading time passing in a process for reading thedocument.
 6. The image reading apparatus according to claim 1, whereinthe control section controls the transport section and the readingsection upon specific low power performance conditions being satisfied,in relevant low power conditions, and obtains the white reference dataand the black reference data when returning from the low powerconditions.
 7. The image reading apparatus according to claim 1, whereinthe controller obtains the black reference data the second case.
 8. Theimage reading apparatus according to claim 7, wherein the controllerdoes not obtain the white reference data and the black reference whenthe image reading apparatus repeatedly reads the transported documents.9. A method for producing an image using an image reading apparatus, themethod comprising: transporting a document with a transporter; readingthe transported document in a transport reading region with a reader;providing white reference material arranged at a position to be read bythe reading section; controlling the transport section and the readingsection with a controller so as to obtain white reference data by makingthe reading section read the white reference material and to obtainblack reference data; obtaining the white reference data when the imagereading apparatus returns from low power mode, and not obtaining thewhite reference data when the image reading apparatus has been a normalpower mode; producing an image from the read transport document.